Tetanus toxin Hc fragment induces the formation of ceramide platforms and protects neuronal cells against oxidative stress

Tetanus toxin (TeTx) is the protein, synthesized by the anaerobic bacteria Clostridium tetani, which causes tetanus disease. TeTx gains entry into target cells by means of its interaction with lipid rafts, which are membrane domains enriched in sphingomyelin and cholesterol. However, the exact mechanism of host membrane binding remains to be fully established. In the present study we used the recombinant carboxyl terminal fragment from TeTx (Hc-TeTx), the domain responsible for target neuron binding, showing that Hc-TeTx induces a moderate but rapid and sustained increase in the ceramide/sphingomyelin ratio in primary cultures of cerebellar granule neurons and in NGF-differentiated PC12 cells, as well as induces the formation of ceramide platforms in the plasma membrane. The mentioned increase is due to the promotion of neutral sphingomyelinase activity and not to the de novo synthesis, since GW4869, a specific neutral sphingomyelinase inhibitor, prevents neutral sphingomyelinase activity increase and formation of ceramide platforms. Moreover, neutral sphingomyelinase inhibition with GW4869 prevents Hc-TeTx-triggered signaling (Akt phosphorylation), as well as the protective effect of Hc-TeTx on PC12 cells subjected to oxidative stress, while siRNA directed against nSM2 prevents protection by Hc-TeTx of NSC-34 cells against oxidative insult. Finally, neutral sphingomyelinase activity seems not to be related with the internalization of Hc-TeTx into PC12 cells. Thus, the presented data shed light on the mechanisms triggered by TeTx after membrane binding, which could be related with the events leading to the neuroprotective action exerted by the Hc-TeTx fragment

Diversity and linkage disequilibrium analysis within a selected set of cultivated tomatoes

Within the Dutch genomics initiative the “Centre for Biosystems Genomics” (CBSG) a major research effort is directed at the identification and unraveling of processes and mechanisms affecting fruit quality in tomato. The basis of this fruit quality program was a diverse set of 94 cultivated tomato cultivars, representing a wide spectrum of phenotypes for quality related traits. This paper describes a diversity study performed on these cultivars, using information of 882 AFLP markers, of which 304 markers had a known map position. The AFLP markers were scored as much as possible in a co-dominant fashion. We investigated genome distribution and coverage for the mapped markers and conclude that it proved difficult to arrive at a dense and uniformly distributed coverage of the genome with markers. Mapped markers and unmapped markers were used to investigate population structure. A clear substructure was observed which seemed to coincide with a grouping based on fruit size. Finally, we studied amount and decay of linkage disequilibrium (LD) along the chromosomes. LD was observed over considerable (genetic) distances. We discuss the feasibility of marker-trait association studies and conclude that the amount of genetic variation in our set of cultivars is limited, but that there exists scope for association studies

End-of-life care and rituals in contexts of post-migration diversity in Europe:An introduction

No abstract available

Genetic dissection of fruit quality traits in the octoploid cultivated strawberry highlights the role of homoeo-QTL in their control

Fruit quality traits are major breeding targets in the Rosaceae. Several of the major Rosaceae species are current or ancient polyploids. To dissect the inheritance of fruit quality traits in polyploid fleshy fruit species, we used a cultivated strawberry segregating population comprising a 213 full-sibling F1 progeny from a cross between the variety ‘Capitola’ and the genotype ‘CF1116’. We previously developed the most comprehensive strawberry linkage map, which displays seven homoeology groups (HG), including each four homoeology linkage groups (Genetics 179:2045–2060, 2008). The map was used to identify quantitative trait loci (QTL) for 19 fruit traits related to fruit development, texture, colour, anthocyanin, sugar and organic acid contents. Analyses were carried out over two or three successive years on field-grown plants. QTL were detected for all the analysed traits. Because strawberry is an octopolyploid species, QTL controlling a given trait and located at orthologous positions on different homoeologous linkage groups within one HG are considered as homoeo-QTL. We found that, for various traits, about one-fourth of QTL were putative homoeo-QTL and were localised on two linkage groups. Several homoeo-QTL could be detected the same year, suggesting that several copies of the gene underlying the QTL are functional. The detection of some other homoeo-QTL was year-dependent. Therefore, changes in allelic expression could take place in response to environmental changes. We believe that, in strawberry as in other polyploid fruit species, the mechanisms unravelled in the present study may play a crucial role in the variations of fruit quality

The <em>fleshless</em> mutation: a valuable source to investigate the regulation of pericarp morphogenesis

The FLESHLESS somatic variation was identified in the grapevine as a chimeric phenotype that develops small fruits with a very little amount of flesh (Fernandez et al., 2006). The lack of flesh development was shown to result from the impairment of both cell division and expansion. Interestingly, the phenotype was found inheritable as a dominant trait, even some phenotypic reversions to the wild-type grapevine berry being observed in the original somatic variant and derived populations. Considering the interest of this phenotypic trait, several experimental approaches were performed to: i) decipher the causal genetic mechanism of the misregulation of the flesh morphogenesis due to flb mutation and ii) identify main genes associated with the fleshless phenotype as potential critical players of early fruit development in the grapevine. Fine mapping using DRCF (Dwarf, Rapid Cycling and Flowering) progenies (Chaib et al., 2010) and gene sequencing identified the insertion of an active MITEs (Miniature Inverted-repeat Transposable Elements) in the promoter of the PISTILLATA-like gene as the original event of the fleshless phenotypic variations. The TE insertion causes specific ectopic activation of a VvPI allele during early fruit development that maintains the expression of floral genes within the fruit. The analysis of transcriptomic patterns induced by the flb mutation into the fruit revealed a set of genes which expression is specific to the transition from flower to young berry development. Some of these genes were functionally characterised, in particular through DRCF genetic transformation. Main outputs of this work will be presented and discussed

The <em>fleshless</em> mutation: a valuable source to investigate the regulation of pericarp morphogenesis

The FLESHLESS somatic variation was identified in the grapevine as a chimeric phenotype that develops small fruits with a very little amount of flesh (Fernandez et al., 2006). The lack of flesh development was shown to result from the impairment of both cell division and expansion. Interestingly, the phenotype was found inheritable as a dominant trait, even some phenotypic reversions to the wild-type grapevine berry being observed in the original somatic variant and derived populations. Considering the interest of this phenotypic trait, several experimental approaches were performed to: i) decipher the causal genetic mechanism of the misregulation of the flesh morphogenesis due to flb mutation and ii) identify main genes associated with the fleshless phenotype as potential critical players of early fruit development in the grapevine. Fine mapping using DRCF (Dwarf, Rapid Cycling and Flowering) progenies (Chaib et al., 2010) and gene sequencing identified the insertion of an active MITEs (Miniature Inverted-repeat Transposable Elements) in the promoter of the PISTILLATA-like gene as the original event of the fleshless phenotypic variations. The TE insertion causes specific ectopic activation of a VvPI allele during early fruit development that maintains the expression of floral genes within the fruit. The analysis of transcriptomic patterns induced by the flb mutation into the fruit revealed a set of genes which expression is specific to the transition from flower to young berry development. Some of these genes were functionally characterised, in particular through DRCF genetic transformation. Main outputs of this work will be presented and discussed